skpyle

Well...Roger got another grand from me.

I looked at all my options, weighed said options, and chose to go back with stock components.

Tuesday, I ordered:
-remanufactured Denso AC compressor
-pressure hose compressor to condensor
-pressure hose compressor to evaporator pipe
-schrader valve cores
-O-ring kit
-expansion valve
-receiver/drier
-low pressure switch
-AC fridgen temp switch
-75C radiator fan switch

I also ordered a new lighted key head and crest...just because.

Most if not all the parts will be here by Saturday. I have ordered a flush gun and gallon of flush solvent. And, today Wally World had cans of R134a on rollback for $4.88 each. I picked up six more cans to have onhand for general principles.

Only thing I am looking for now is a fish scale. I have read that the stock R12 fill is 36 ounces, and 85% fill for R134a is 30 ounces, or 2.5 cans. My calibrated hand is lousy at weighing things. So, I am going to find a fish scale to measure the weight of the thirc can, and go from there.


Seth K. Pyle

FredR

Not sure if I missed something but how did you arrive at needing a rebuilt or new compressor?

Not saying it is "not a good idea" and fully support the notion of going through the system lock stock and barrel as you appear to be.

As a general comment I noted Joel's comment about fitting a relay to supply power to the solenoid. I have been contemplating doing this as the solenoid takes quite a lot of amps [I seem to remember] and if the head relay is wobbling at bit [as mine now is] it may well help matters. If anyone has the spec for such a relay that would be helpful.

Regarding the optional rear a/c I reckon this is a double edged thing. When you are in hot temps like I am the rear a/c simply robs effect from the front a/c as the condenser surface area is the limiting factor for capacity. The automatics with the tranny oil cooler are robbed of surface area having a smaller condenser compared to the manuals [GTS manuals excepted as they have an oil cooler as well].

Rgds


Fred

skpyle

Hello FredR: You didn't miss anything.

I have been thinking my way through this for the past several days.
I believe the current point of failure is going to be the compressor seal. This is based partly on a hunch and partly on a WAG.
The compressor has been used very little in the past years because the car has been driven very little.
Shop runs compressor to check AC.
I run the AC for a few hours on the road trip home.
No more AC after that due to system is empty of refrigerant.

So, I am doing an overhaul based on the following points:
-R134a conversion is 15 years old
-compressor is original
-hoses are original

I plan on keeping the Red Witch indefinitely. Working AC is not optional for me. Therefore, it is worth my time and money to fix it right. In my mind, an AC compressor is a long term consumable item. It doesn't last forever. 30 years seems like a good time to change it.
The only caveat is the long evaporator hose. I have not found any mobile services that do onsite AC hose crimping.
If that hose has ruptured, I am stuck until I come up with another plan.

Very good point about rear AC. The evaporator area is increased, but condenser area is the same. I have seen mention of a kit that adds a second condenser to the system. Spendy $$$.

I am going to overhaul this system and go from there.


Thanks!
Seth K. Pyle

FredR

Seth,

You have me lost regarding the "Long evaporator hose". As I am aware there are only two hoses - these to/from the compressor to allow flexure in the system.

I had an annoying leak up to about 2 or so years ago needing to top up every so often. I rely on dye to find leaks and what we eventually found was leaks from the compressor body seals. We have some problems out here with spare parts and capabilities but one thing we are blessed with are a/c experts [surprise surprise]. I removed the compressor from the car, took it to a little shop 5 minutes walk from my house and they pulled the compressor apart, cleaned everything, fitted new bearings, new dynamic seal and body seals and fitted a new solenoid clutch- cost me about $120 all in. On tht occasion I won out.

When everything is working correctly with 134 the system works very well up to about 40C. Once the needle goes north of that the performance drops noticeably but I have been comfortable when cruising at 44C [like it is now]- in stop go traffic it is decidedly dodgy though.

Good to see your enthusiasm. I hope you will be rewarded.

Rgds

Fred

Adk46

My compressor has green stuff beneath the shaft seal. For some time, I thought it was anti-freeze running down from above somewhere, but it appears to be dye from previous leak-detection efforts.

Roger told me his customers are often disappointed with the long-term results of a DIY overhaul, so I will soon get a rebuilt unit, bolt it in myself, take it to an AC shop for proper flushing and filling, and buy a lottery ticket.

With your approach, Seth, you might be able to dispense with the lottery ticket.

Imo000

If you didn't properly diagnose the AC leak then you are just randomly throwing parts at it. You might get lucky and fix the leak but this isn't the best way to do this. How are you planning to pull the vacuum? Didn't see the pump on the list of your parts. My educated guess on why the system leaked was that the shop filled it up just before you left.

skpyle

Thank you so much for the vote of confidence.

You didn't see a vacuum pump on the list because I already have one, an electric motor driven pump.
And a set of manifold gauges.
And a can tap.
And a sniffer.
And a Fluke digital thermometer.
And safety goggles.
And neoprene gloves.
And a 24" floor fan for airflow across the condenser for testing.
And some experience troubleshooting automotive AC systems.
I am by no means an expert, but I do OK.

I did not go into diagnostics because I have a reasonable idea what caused a complete loss of refrigerant overnight. PO recharged the system earlier this year. Could have been empty, I don't know. Auto Assets did not add any refrigerant. How do I know? Because they would have charged me for it. They did everything else.

I strongly suspect the 30 year old compressor seal failed due to years of inactivity followed by hours of use. Could I be wrong? Of course.
Hence, my decision to overhaul the system. I am 'throwing parts at it' in a controlled manner, from advice from numerous sources, and my own experience. I am looking at points of failure.
-compressor
-hoses
-O-rings
-expansion valve
-receiver/drier
-switches

Yes, there are things that could still bite me in the ***:
Evaporator core
Condenser
Fuel cooler
Long evaporator hose

Of those, the evaporator hose is most likely to be an issue. However, I am betting it is serviceable for now. I am willing to take that gamble. If it blows up in my face, I fall back and punt. As of this point, I have not found a local shop that can crimp a new section of barrier hose to the evaporator line in place. I am not pulling the engine to replace the line.
I am rolling the dice and hoping I don't get snake eyes.

In addition, I am basing the decision to go straight to overhaul based upon time. I don't have as much as I would like. For various reasons and issues, I have not been able to leave work on time any day this week. Plus, I have had numerous issues to deal with here at the house. So, no time to troubleshoot.
I start on the AC and belt tension check in the morning. I am going to make what I think is the best use of my time.

One of two things will happen:
1) The Red Witch will have frosty cold AC.
2) I will figure out how to deal with whatever else has gone wrong.


Thank you.

Seth K. Pyle

dr bob

Fred--

My clutch coil measured about 4 Ohms on the meter, and, amazingly, it's an inductive load. The original head relay is rated at 2 Amps or so IIRC, but that's for AC. So basically under rated and not suitable for the DC kick when it opens.

Depending on mounting location and connection method, physical size may or may not matter. In my fitment, I was interested in keep the relay with the head unit, so there is no modification to the car's wiring or connectors, and no jury-rigged hang-on box taped up near the jump post. I chose a DPDT relay I found at a parts place, with contacts rated at 20A DC. Figured I wouldn't need to worry ever again. It's wired to replace the original board-mounted relay, but pigtailed out of the head unit case. I was shopping for size as well as capacity , in consideration of the very limited space available immediately outside the head unit.

If you plan to mount a relay that's actuated by your still-functional head unit, you can use the very standard Bosch 53B flavor mounted almost anywhere between the head unit and the clutch coil. Alan made a point that the wiring to the freeze switch and the clutch coil passes through the CE panel for the suppressor, so that would be a great place to put an accessory relay.

bureau13

My only concern would be that if (for example) you've simply sprung a leak at the expansion valve, you've spent a lot of extra money and done a lot of extra work. Even worse, if it's the condenser or evaporator, you've done that and not fixed the problem. Leak tests can generally be performed by any decent shop. That being said, you're correct about 30 year old parts, and compressors and those flexible hoses failing are very likely culprits. Even if they're not the source of your leak, they could easily be next year. You're unlikely to do anything but improve the system by replacing that stuff. But knowing exactly where it's leaking would still be good information, just sayin...

skpyle

FredR: There is a third line in the system. It is a metal line that runs from the evaporator to the receiver/drier, along the passenger's side of the engine compartment. Near the front of the engine, there is an approximately 6" long section of hose in this metal line. The line is item #33 on PET, Body, Porsche 928 Refrigerant Circuit.

People commonly have this line rebuilt with new hose and crimp ferrules. This line can only be removed when the engine is out.
Greg Brown has a repair kit that requires the metal line to be silver soldered.
Others have reported having a mobile hose service crimp new ferrules and a new section of barrier hose to the line.

I believe the system will work well once done. I am very familiar with how an AC system is less effective at idle due to reduced air flow across the condenser.
Thanks!



Adk46: I have seen the green slime before. Yuck. I had considered rebuilding the compressor myself. However, it is 30 years old, and I am not sure what kind of wear I am going to find inside. Peace of mind for me to go with a factory reman compressor. Good to know about Roger's perspective.
Thank you for the support.



dr bob: Thanks for the heads-up on the 53B relay in the CE panel for the upgrade for the clutch coil. That makes more sense than my approach of wiring a relay in the engine compartment.
As of right now, the HVAC relay is still functioning on the controller for the Red Witch. I have ordered a similar relay that you did. At some point in the near future I will install it.



bureau13: I thought about that as well. Right now, I am gambling on the failure is the common compressor seal and/or failed O-rings. If it is the condenser, I will get another one, possibly an uprated parallel flow unit. If it is the evaporator...I will cry.
I have spent a great deal of money on this AC overhaul, but I believe it is worth it. I am returning the system to a point of usefulness and reliability, I hope.
Right this moment, I am of two minds:
If it is still raining in the morning enough that I am not comfortable jacking the Red Witch up and starting to tear her apart, I will charge the AC and do some 'sniffering.'
If it is nice, I will start the overhaul work.
Either way, something is going to happen.


Thanks!

Seth K. Pyle

FredR

Seth,

Thanks for the clarification- see you are an expert already!

I have never noticed the "hose" section you refer. I wonder if your model year is different compared to later models [doubt it]?

Bob,

Sounds as though you did something along the lines Dwayne did in his write up. Same config but with beefier relay. I considered that but did not like the soldering involved [not my greatest skill].

I knew the solenoid took some ampage but 4 amps- wow! Not difficult to see why my head relay might be sweating especially in our ambients. Sounds as though a separate feed to the clutch would need a 5 amp fuse minimum. Given the current actuating cable runs from the 14 pin connector to the a/c clutch I was thinking of interdicting it at that location and running a cable with inline fuse from the hot post to the clutch. Thus my perceived need for a relay that can withstand the engine bay temps in that locale.

I have a spare head unit from my S4 but that is featured slightly different as the GTS unit has an additional feature. Whether it would plug and play without the additional feature I have no idea and would not try without an informed opinion.

Clearly I need to rethink this a bit more.

Rgds

Fred

bureau13

The weird thing about this relay...I had a controller failure, and assumed it was the relay. However, the relay on my board said it was a 5A part. I had purchased a Radio Shack relay that had been recommended for this use, but didn't put it on, as the problem was actually with a poor previous repair of a burned trace. I could never get any info on whether these things ever came stock with a 5A relay. It did not look obviously after-market, but someone had clearly been in there before due to the repair attempt...

dr bob

Fred--

My effort predates Dwayne's by a bit. He offered a more detailed "how to do it" vs my original "what I did". Mine was not originally intended to be an instruction, but rather documentation of a specific modification I made to the car, added to the log book/documentation package. Having been the victim of poor documentation on other "interesting" cars, I decided long ago that I will never be that $&(*!!! PO who cut and spliced to add accessories or make "improvements" or other modifications. For the head unit, my goal was/is to have a mod that's easily returnable to factory condition. So I bought a used working head unit to add to the original-parts-removed bin. Then modified mine.

Jeff-- Greg Brown promotes adding an inline fuse for the clutch coil circuit to protect the head unit circuitry. Seems a good idea, especially looking at the number of PC traces that have been sacrificed to protect the external wiring.

bureau13

That sounds like a good idea. I'll research this...

FredR

Bob,

I have a spare head unit from my S4 but the functionality is slightly different on the GTS to the earlier models. Much appreciate if you [or anyone else] can opine on whether I can slip this unit in and it will still work without anything going pop. I never use the additional feature [it has a circular icon] and would be quite happy if it functions same as the S4 but no idea whether it is plug and play or everything catches fire and melts.

Rgds

Fred